Rabies: The risk is real

A beef cow acting bizarrely in a small cow-calf herd. A skunk attacking heifers and dry cows in a large, commercial dairy. A raccoon attacking the family dog.

What do these cases have in common? All are confirmed cases of rabies occurring in the past 2 months within our northern New York practice area. The resurgence reminds us the risk is real.

Rabies – a viral disease causing inflammation of the brain and eventual death – is generally not considered a disease of humans. Rather, it’s seen as an animal disease that can be transmitted to humans by a bite or scratch, exposing the person to infected saliva. In recent years there have been less than three deaths annually in the U.S. attributed to this virus. However, in less-developed countries there are estimates of more than 55,000 deaths per year.

Within livestock and pets, the rabies vaccine has been proven to be safe and efficacious, and is always administered as a pre-exposure vaccination to prevent the disease.

In humans, there are options of both pre- and postexposure vaccination, and also the administration of human rabies immune globulin. Think of immune globulin as an injectable colostrum, rich in antibodies to attack the virus after known exposure, but before it reaches and infects the brain cells.

Raising awareness

Given that rabies is essentially always fatal – there’s only one confirmed human case of rabies virus survival – it is imperative that people at risk are aware of the basics, and take necessary precautions.

Rabies signs start with fever, depression and loss of appetite,

progressing to neurological problems, including an inability to rise, and eventual death. The cow is generally considered a dead-end host for the virus; it is unlikely she will transmit it to another animal or human via a bite.

People can be exposed, however, during the treatment of infected cattle, especially if exposed to the saliva through a cut or scratch. We should try to limit the number of individuals responsible for treating or handling a neurologic cow. Wear gloves and, ideally, face/eye protection to prevent contact with saliva during routine procedures. Given these cows are generally “off-feed”, it is common to drench them, leading to saliva exposure.

In the event of a cow’s death or euthanasia possibly related to rabies, brain tissue must be preserved for testing. Consultation with your veterinarian is important, especially in cases of possible human exposure.

Vaccination: Cattle or workers?

Should we vaccinate our livestock or workers? This is an excellent question, and the answer is not simple.

We have traditionally associated vaccinating livestock with protecting farm workers. We do not want to lose a cow or heifer to rabies – and deal with state quarantine issues – but the real concern is human exposure.

In many states, rabies vaccination can only be administered by a licensed veterinarian, adding another level of complexity to the decision. And, in cattle, annual revaccination is necessary.

Given the cost and labor for vaccinating a herd, a reasonable option would be to provide pre-exposure vaccination to at-risk workers. A simple partial budget analysis would suggest this to be a sound economic and public health decision.

High-risk individuals – veterinarians, animal handlers and laboratory personnel – are routinely vaccinated. In the past we have not considered herdspeople or other livestock workers at risk, but the recent cases in our region have caused us to rethink this. Once a person is vaccinated, the need for routine boosters is unlikely.

Historically we have been less concerned with livestock exposure, especially in large, commercial dairy operations. The recent events in our region remind us that no size operation is immune to potential exposure.

The aggressive skunk in the freestall is not common, but what if

this critter came in during the night, bit a number of cattle and was never seen? Upfront knowledge can reduce headaches and save money in the event of human exposure to a rabid animal.

Mark Thomas is a veterinarian and owner of Dairy Health & Management Services, LCC and Countryside Veterinary Clinic, LLP, Lowville, N.Y. He is currently vice president of the American Association of Bovine Practitioners. Contact him via e-mail at mthomas@dairyhealthmanagement.com.